Field of the Invention
The present invention relates to an image inspection apparatus that optically reads an image and determines the line width of the image, and an image forming apparatus that determines the line width of an image and sets an output for image writing in accordance with the line width.
Description of the Related Art
An apparatus that optically reads an image formed on a medium such as a paper sheet digitizes the read image or determines whether the formed image is correctly written. In view of this, techniques for correct image recognition have been suggested.
According to one of the suggested techniques, an apparatus that reads one- or two-dimensionally coded information such as a bar code determines whether there is a blur in a read image, and determines whether the distance from the apparatus to the object to be read falls within such a range as to perform appropriate reading (see JP 2006-209208 A, for example).
For an apparatus that reads bar codes, the following technique has been suggested. A bar code is formed with black lines and white lines that are alternately arranged, and the line widths of black lines and white lines are integral multiples of the smallest line width. Line width recognition is performed by taking advantage these characteristics, after the image is subjected to black/white determination with a predetermined threshold value (see JP 62-120585 A, for example).
In a process to determine the line width of a linear image from image data obtained by optically reading the image, the edges of the image are detected, and the distance between the edges is determined. In this manner, the line width is obtained. When the distance between the image to be read and the optical reading unit changes, the image data is blurred, and edges are not accurately detected from the image data. As a result, the obtained line width differs from the actual value.
For example, there is a technique by which an output for image writing is set, an image is set, and the line width of the formed image is determined. The relationship between the output for image writing and the line width of the formed image is then determined, so that an appropriate output for image writing for forming an image with a predetermined line width is set. By this technique, however, a correct output for image writing is not set unless the line width is correctly determined.
By any of the techniques disclosed in the prior art documents mentioned above, a correct line width is not obtained when the distance between the image to be read and the optical reading unit changes.